#!/usr/bin/env python3
"""
GitHub App User Token Generator

Generates repo-scoped GitHub user access tokens via the device flow.
Only requires the GitHub App's Client ID (no secrets needed).

Usage:
  # Print instructions to create the GitHub App (one-time setup)
  python3 github_app_token_demo.py create-app

  # Generate a user access token via device flow
  python3 github_app_token_demo.py user-token --client-id Iv23liXXXXXX

  # Scope the token to a single repo (writes only)
  python3 github_app_token_demo.py user-token --client-id Iv23liXXXXXX --repo wirenboard/agent-vm

Add -v/--verbose to any command for detailed HTTP logging.
"""

import argparse
import json
import os
import sys
import re
import time
import urllib.parse
import urllib.request
import urllib.error

TARGET_OWNER = os.environ.get("TARGET_OWNER", "wirenboard")
TARGET_REPO = os.environ.get("TARGET_REPO", "agent-vm")

VERBOSE = False

# Retry settings for transient GitHub errors (5xx)
MAX_RETRIES = 3
RETRY_DELAYS = [1, 2, 4]
ERROR_LOG_DIR = os.environ.get("GITHUB_TOKEN_LOG_DIR", ".")


def verbose(msg):
    if VERBOSE:
        print(f"  [verbose] {msg}", file=sys.stderr)


def _looks_like_html(body_str):
    """Check if a response body is HTML."""
    prefix = body_str[:256].lstrip()
    return prefix.startswith(("<", "<!DOCTYPE", "<!doctype"))


def _save_error_body(status, body_str, context=""):
    """Save an error response body to a file for debugging. Returns the path."""
    ts = time.strftime("%Y%m%d-%H%M%S")
    filename = f"github-token-error-{ts}-{status}.html"
    path = os.path.join(ERROR_LOG_DIR, filename)
    try:
        with open(path, "w") as f:
            if context:
                f.write(f"<!-- {context} -->\n")
            f.write(body_str)
        verbose(f"saved error response to {path}")
    except OSError as e:
        verbose(f"failed to save error response: {e}")
        path = None
    return path


def _copy_to_clipboard(text):
    """Try to copy text to the system clipboard. Fails silently."""
    import subprocess
    import shutil
    for cmd in (["pbcopy"], ["xclip", "-selection", "clipboard"], ["xsel", "--clipboard", "--input"], ["wl-copy"]):
        if shutil.which(cmd[0]):
            try:
                subprocess.run(cmd, input=text.encode(), check=True, timeout=5)
                verbose(f"copied to clipboard via {cmd[0]}")
                return True
            except (subprocess.SubprocessError, OSError):
                pass
    verbose("no clipboard tool found")
    return False


def parse_repo(repo_str):
    """Parse a repo URL/slug into (owner, name). Accepts:
    - owner/name
    - https://github.com/owner/name
    - git@github.com:owner/name.git
    """
    # git@github.com:owner/name.git
    m = re.match(r'git@github\.com:([^/]+)/([^/]+?)(?:\.git)?$', repo_str)
    if m:
        return m.group(1), m.group(2)
    # https://github.com/owner/name[.git]
    m = re.match(r'https?://github\.com/([^/]+)/([^/]+?)(?:\.git)?(?:/.*)?$', repo_str)
    if m:
        return m.group(1), m.group(2)
    # owner/name
    m = re.match(r'^([^/]+)/([^/]+)$', repo_str)
    if m:
        return m.group(1), m.group(2)
    print(f"Error: cannot parse repo: {repo_str}", file=sys.stderr)
    sys.exit(1)


def resolve_repo_id(owner, name):
    """Resolve a repo's numeric ID. Tries public API first, falls back to gh CLI."""
    import subprocess

    url = f"https://api.github.com/repos/{owner}/{name}"
    req = urllib.request.Request(url)
    req.add_header("Accept", "application/vnd.github+json")
    verbose(f"Resolving repo ID: {owner}/{name}")
    try:
        with urllib.request.urlopen(req) as resp:
            data = json.loads(resp.read().decode())
            repo_id = data["id"]
            verbose(f"Resolved {owner}/{name} -> {repo_id}")
            return str(repo_id)
    except urllib.error.HTTPError:
        verbose(f"Public API failed, trying gh CLI...")
        try:
            result = subprocess.run(
                ["gh", "api", f"repos/{owner}/{name}", "--jq", ".id"],
                capture_output=True, text=True, check=True,
            )
            repo_id = result.stdout.strip()
            verbose(f"Resolved {owner}/{name} -> {repo_id} (via gh)")
            return repo_id
        except (subprocess.CalledProcessError, FileNotFoundError) as e:
            print(f"Error: cannot resolve repo {owner}/{name}", file=sys.stderr)
            print(f"  Public API returned 404 and gh CLI failed: {e}", file=sys.stderr)
            print(f"  Use --repository-id to pass the numeric ID directly", file=sys.stderr)
            sys.exit(1)


# --- App creation helper ---

APP_MANIFEST = {
    "name": "WB Agent VM Token Generator",
    "url": "https://github.com/wirenboard/agent-vm",
    "hook_attributes": {"active": False},
    "redirect_url": "",
    "public": False,
    "default_permissions": {"contents": "write"},
    "default_events": [],
}


def cmd_create_app():
    """Print instructions for creating the GitHub App via the UI."""
    print("=" * 60)
    print("GitHub App Creation Instructions")
    print("=" * 60)
    print()
    print("1. Go to: https://github.com/organizations/wirenboard/settings/apps/new")
    print("   (Or for personal account: https://github.com/settings/apps/new)")
    print()
    print("2. Fill in the following settings:")
    print(f"   - GitHub App name: {APP_MANIFEST['name']}")
    print(f"   - Homepage URL: {APP_MANIFEST['url']}")
    print("   - Uncheck 'Active' under Webhook")
    print("   - Under 'Repository permissions':")
    print("     - Contents: Read & write")
    print("   - Under 'Where can this GitHub App be installed?':")
    print("     - Select 'Only on this account'")
    print()
    print("   After creating the app, go to Optional features:")
    print("     - User-to-server token expiration: Opt-out")
    print("     (Expiring tokens break when multiple repos are used,")
    print("      because each device flow revokes previous refresh tokens)")
    print()
    print("3. Click 'Create GitHub App'")
    print()
    print("4. Note the Client ID (starts with Iv...)")
    print()
    print("5. Install the app:")
    print("   - Click 'Install App' in the left sidebar")
    print("   - Choose the target organization/account")
    print("   - Select repositories to grant access to")
    print()
    print("6. Generate a token:")
    print(f"   python3 {sys.argv[0]} user-token --client-id <CLIENT_ID> --repo <owner/repo>")
    print()


# --- GitHub API helper ---


def github_api(method, path, token, token_type="Bearer", body=None):
    """Make a GitHub API request with retry on 5xx errors."""
    url = f"https://api.github.com{path}"
    data = json.dumps(body).encode() if body else None

    verbose(f">>> {method} {url}")
    if body:
        verbose(f">>> Body: {json.dumps(body)}")

    last_error = None
    for attempt in range(MAX_RETRIES + 1):
        if attempt > 0:
            delay = RETRY_DELAYS[min(attempt - 1, len(RETRY_DELAYS) - 1)]
            verbose(f"retry {attempt}/{MAX_RETRIES} after {delay}s")
            time.sleep(delay)

        req = urllib.request.Request(url, data=data, method=method)
        req.add_header("Accept", "application/vnd.github+json")
        req.add_header("Authorization", f"{token_type} {token}")
        req.add_header("X-GitHub-Api-Version", "2022-11-28")
        if data:
            req.add_header("Content-Type", "application/json")

        try:
            with urllib.request.urlopen(req) as resp:
                resp_body = resp.read().decode()
                verbose(f"<<< {resp.status} {resp.reason}")
                verbose(f"<<< Body: {resp_body[:500]}{'...' if len(resp_body) > 500 else ''}")
                return json.loads(resp_body)
        except urllib.error.HTTPError as e:
            error_body = e.read().decode()
            verbose(f"<<< {e.code} {e.reason}")
            verbose(f"<<< Body: {error_body}")
            if e.code >= 500:
                if _looks_like_html(error_body):
                    _save_error_body(e.code, error_body, f"{method} {url} attempt {attempt + 1}")
                    last_error = f"{e.code} {e.reason} (HTML error page saved to disk)"
                else:
                    last_error = f"{e.code} {e.reason}"
                print(f"GitHub API error: {e.code} {e.reason} (attempt {attempt + 1}/{MAX_RETRIES + 1}, retrying...)", file=sys.stderr)
                continue
            # Non-5xx error — don't retry
            print(f"GitHub API error: {e.code} {e.reason}", file=sys.stderr)
            print(f"URL: {url}", file=sys.stderr)
            if _looks_like_html(error_body):
                saved = _save_error_body(e.code, error_body, f"{method} {url}")
                print(f"Response body saved to: {saved}", file=sys.stderr)
            else:
                print(f"Response: {error_body}", file=sys.stderr)
            sys.exit(1)
        except urllib.error.URLError as e:
            last_error = str(e.reason)
            print(f"GitHub API error: {last_error} (attempt {attempt + 1}/{MAX_RETRIES + 1}, retrying...)", file=sys.stderr)
            continue

    print(f"GitHub API error: {last_error} (all {MAX_RETRIES + 1} attempts failed)", file=sys.stderr)
    print(f"URL: {url}", file=sys.stderr)
    sys.exit(1)


def verify_token(token, token_type="token"):
    """Verify the token works by reading the target repo."""
    repo = github_api(
        "GET",
        f"/repos/{TARGET_OWNER}/{TARGET_REPO}",
        token,
        token_type=token_type,
    )
    return repo


# --- Token cache ---

DEFAULT_CACHE_DIR = os.path.expanduser("~/.cache/claude-vm")


def _cache_path(cache_dir, client_id, owner, repo):
    """Return the cache file path for a given client/repo combo."""
    safe = f"{owner}_{repo}".replace("/", "_")
    return os.path.join(cache_dir, f"github-token-{safe}.json")


def load_cached_token(cache_dir, client_id, owner, repo):
    """Try to load a valid token from cache. Returns token string or None."""
    path = _cache_path(cache_dir, client_id, owner, repo)
    try:
        with open(path, "r") as f:
            data = json.load(f)
    except (FileNotFoundError, json.JSONDecodeError):
        return None

    token = data.get("access_token")
    if not token:
        return None

    # Discard old-format cache files that had expiring tokens
    if data.get("refresh_token") or data.get("expires_at"):
        verbose("Discarding old cache with expiring token format")
        try:
            os.unlink(path)
        except OSError:
            pass
        return None

    verbose(f"Using cached token")
    return token


def save_cached_token(cache_dir, client_id, owner, repo, access_token):
    """Save token to cache file."""
    path = _cache_path(cache_dir, client_id, owner, repo)
    os.makedirs(os.path.dirname(path), exist_ok=True)
    data = {"access_token": access_token}
    with open(path, "w") as f:
        json.dump(data, f)
    # Restrict permissions — token file
    os.chmod(path, 0o600)
    verbose(f"Token cached to {path}")


# --- Device flow (user access token) ---


def device_flow_request(url, params):
    """POST to GitHub's OAuth endpoints (form-encoded, JSON response).
    Retries on 5xx errors; saves HTML error pages to disk."""
    encoded_data = urllib.parse.urlencode(params).encode()

    verbose(f">>> POST {url}")
    verbose(f">>> Body: {urllib.parse.urlencode(params)}")

    last_error = None
    for attempt in range(MAX_RETRIES + 1):
        if attempt > 0:
            delay = RETRY_DELAYS[min(attempt - 1, len(RETRY_DELAYS) - 1)]
            verbose(f"retry {attempt}/{MAX_RETRIES} after {delay}s")
            time.sleep(delay)

        req = urllib.request.Request(url, data=encoded_data, method="POST")
        req.add_header("Accept", "application/json")

        try:
            with urllib.request.urlopen(req) as resp:
                resp_body = resp.read().decode()
                verbose(f"<<< {resp.status} {resp.reason}")
                verbose(f"<<< Body: {resp_body[:500]}{'...' if len(resp_body) > 500 else ''}")
                return json.loads(resp_body)
        except urllib.error.HTTPError as e:
            error_body = e.read().decode()
            verbose(f"<<< {e.code} {e.reason}")
            verbose(f"<<< Body: {error_body}")
            if e.code >= 500:
                if _looks_like_html(error_body):
                    _save_error_body(e.code, error_body, f"POST {url} attempt {attempt + 1}")
                    last_error = f"{e.code} {e.reason} (HTML error page saved to disk)"
                else:
                    last_error = f"{e.code} {e.reason}"
                print(f"  GitHub returned {e.code} (attempt {attempt + 1}/{MAX_RETRIES + 1}, retrying...)", file=sys.stderr)
                continue
            # Non-5xx error — don't retry
            print(f"GitHub OAuth error: {e.code} {e.reason}", file=sys.stderr)
            if _looks_like_html(error_body):
                saved = _save_error_body(e.code, error_body, f"POST {url}")
                print(f"Response body saved to: {saved}", file=sys.stderr)
            else:
                print(f"Response: {error_body}", file=sys.stderr)
            sys.exit(1)
        except urllib.error.URLError as e:
            last_error = str(e.reason)
            print(f"  Connection error: {last_error} (attempt {attempt + 1}/{MAX_RETRIES + 1}, retrying...)", file=sys.stderr)
            continue

    print(f"GitHub OAuth failed: {last_error} (all {MAX_RETRIES + 1} attempts failed)", file=sys.stderr)
    sys.exit(1)


def cmd_user_token(client_id, repository_id=None, token_only=False,
                   cache_dir=None):
    """Generate a user access token via the device flow."""
    out = sys.stderr if token_only else sys.stdout

    # Try cached token first
    if cache_dir:
        cached = load_cached_token(cache_dir, client_id, TARGET_OWNER, TARGET_REPO)
        if cached:
            print(f"Using cached token for {TARGET_OWNER}/{TARGET_REPO}", file=out)
            if token_only:
                print(cached)
            else:
                print("=" * 60)
                print(f"GITHUB_TOKEN={cached}")
                print("=" * 60)
            return

    print("Requesting device code...", file=out)
    resp = device_flow_request(
        "https://github.com/login/device/code",
        {"client_id": client_id},
    )

    device_code = resp["device_code"]
    user_code = resp["user_code"]
    verification_uri = resp["verification_uri"]
    expires_in = resp["expires_in"]
    interval = resp.get("interval", 5)

    verbose(f"Device code: {device_code}")
    verbose(f"Polling interval: {interval}s, expires in: {expires_in}s")

    # Copy the user code to clipboard if possible
    copied = _copy_to_clipboard(user_code)
    clip_hint = " (copied to clipboard)" if copied else ""

    print(file=out)
    print("=" * 60, file=out)
    print(f"  Open:  {verification_uri}", file=out)
    print(f"  Enter: {user_code}{clip_hint}", file=out)
    print("=" * 60, file=out)
    print(file=out)
    print(f"Waiting for authorization (expires in {expires_in}s)...", file=out)

    # Poll for the token
    poll_count = 0
    while True:
        time.sleep(interval)
        poll_count += 1
        verbose(f"Polling attempt #{poll_count}...")
        poll_params = {
            "client_id": client_id,
            "device_code": device_code,
            "grant_type": "urn:ietf:params:oauth:grant-type:device_code",
        }
        if repository_id:
            poll_params["repository_id"] = repository_id
        token_resp = device_flow_request(
            "https://github.com/login/oauth/access_token",
            poll_params,
        )

        error = token_resp.get("error")
        if error == "authorization_pending":
            verbose("Status: authorization_pending")
            continue
        elif error == "slow_down":
            interval = token_resp.get("interval", interval + 5)
            verbose(f"Status: slow_down, new interval: {interval}s")
            continue
        elif error == "expired_token":
            print("Error: Device code expired. Please try again.", file=sys.stderr)
            sys.exit(1)
        elif error == "access_denied":
            print("Error: Authorization was denied by the user.", file=sys.stderr)
            sys.exit(1)
        elif error:
            print(f"Error: {error} - {token_resp.get('error_description', '')}", file=sys.stderr)
            sys.exit(1)

        # Success
        token = token_resp["access_token"]
        token_type = token_resp.get("token_type", "bearer")
        verbose(f"Token type: {token_type}")
        verbose(f"Full token response keys: {list(token_resp.keys())}")
        break

    print("Authorization successful!", file=out)
    print(file=out)

    print("Verifying token...", file=out)
    repo = verify_token(token, token_type="Bearer")
    print(f"Verified: can access {repo['full_name']}", file=out)
    print(file=out)

    # Cache the token
    if cache_dir:
        save_cached_token(cache_dir, client_id, TARGET_OWNER, TARGET_REPO,
                          token)

    if token_only:
        print(token)
    else:
        print("=" * 60)
        print(f"GITHUB_TOKEN={token}")
        print("=" * 60)


# --- CLI ---


def main():
    global VERBOSE

    parser = argparse.ArgumentParser(
        description="Generate repo-scoped GitHub user tokens via a GitHub App"
    )
    parser.add_argument("-v", "--verbose", action="store_true",
                        help="Enable verbose HTTP logging to stderr")
    sub = parser.add_subparsers(dest="command")

    sub.add_parser("create-app", help="Print instructions to create the GitHub App")

    user_parser = sub.add_parser("user-token", help="Generate a user access token via device flow")
    user_parser.add_argument("--client-id", required=True, help="GitHub App Client ID (Iv23li...)")
    user_parser.add_argument("--repo", type=str, default=None,
                             help="Repository to scope the token to (owner/name, URL, or git@github.com:owner/name.git)")
    user_parser.add_argument("--repository-id", type=str, default=None,
                             help="Numeric repo ID (use for private repos where --repo can't resolve)")
    user_parser.add_argument("--token-only", action="store_true",
                             help="Print only the token to stdout (status messages go to stderr)")
    user_parser.add_argument("--cache-dir", type=str, default=None,
                             help="Directory to cache tokens (default: no caching)")

    args = parser.parse_args()
    VERBOSE = args.verbose

    if args.command == "create-app":
        cmd_create_app()
    elif args.command == "user-token":
        global TARGET_OWNER, TARGET_REPO
        repository_id = args.repository_id
        if args.repo:
            TARGET_OWNER, TARGET_REPO = parse_repo(args.repo)
            if not repository_id:
                repository_id = resolve_repo_id(TARGET_OWNER, TARGET_REPO)
        cmd_user_token(args.client_id, repository_id=repository_id,
                       token_only=args.token_only,
                       cache_dir=args.cache_dir)
    else:
        parser.print_help()
        sys.exit(1)


if __name__ == "__main__":
    main()